Health care is undergoing a major transition from generic solutions to research-supported personalized health care, which aims to develop prevention and treatment strategies directed by individual characteristics. There is an acute need for such treatment approaches in hearing health care, where hearing aids (the primary treatment for hearing loss) have had limited acceptance and uncertain individual benefits. The proposed work encompasses three sets of experiments that take a systematic approach to prescribing hearing aid signal processing customized to the listener's abilities. The first specifi aim is to describe how the listener profile determines response to hearing aid signal processing in quiet and in adverse listening environments. The focus is on the core technology decisions that must be made by clinical audiologists: the speed of the wide- dynamic range compressor; the number of compression channels; and the use of frequency lowering. The project will combine behavioral measurements and signal analysis, using an auditory model (the Spectral Correlation Index) to understand the effect of acoustic changes imposed by signal processing. It is hypothesized that listeners who rely on different aspects of the speech signal will also respond differently to specific hearing-aid signal processing, and that customizing signal processing to the listener profile will result in improved speech intelligibility compared to other signal processing options. It is also hypothesized that reduced acoustic redundancy - as will occur in reverberation and background noise - will magnify the effect of signal processing distortions. The second specific aim will relate listener profile to performance on a set of psychoacoustic measures that also test sensitivity to temporal and spectral cues. This will allow differentiation between listeners who use particular cue patterns because they cannot access others, versus as a preference or adaptation. It is hypothesized that while all listeners will demonstrate cue profiles that are not well predicted by their audiograms, listeners with poorer spectral resolution and those with severe loss will be more likely to rely on temporal cues to speech. It is anticipated that the outcome of this aim will support a refined version of the profil, including a set of clear clinical guidelines. The third specific aim is to demonstrate the consequences of profile-directed signal processing for speech perception in everyday listening and under clinical fitting conditions with wearable hearing aids. Simulated reverberant and noisy environments will be created in Northwestern's Virtual Sound Room. Speech intelligibility and quality will be compared for profile-directed and profile-misdirected processing, as well as standard-of-care fitting (the listeners' own aids). It is hypothesized that the relationships demonstrated in Aim 1 will be present in everyday environments and under the constraints and acoustic properties created by wearable hearing aids. Taken together, the questions addressed in this project will provide a comprehensive assessment of the effects of hearing aid processing in realistic listening environments, while considering specific abilities that affect response to signal processing.